Automatic switch control means for kilns



April 0, 1954 w. P. DAWSON 2,675,600

AUTOMATIC SWITCH CONTROL MEANS'FOR KILNS Filed Aug. 8. 1952 2 Sheets-Sheet l IN VEN TOR.

WILFREO P. DAWSON.

ATTOR NFY April 20, 1954 w DAWSON 2,675,600

AUTOMATIC SWITCH CONTROL MEANS FOR KILNS Filed Aug. 8, 1952 2 Sheets-Sheet 2 I gll l2 INVENTOR. WILFRED P- DAW Patented Apr. 20, 1954 UNITED STATES PATENT OFFICE AUTOMATIC SWITCH CONTROL MEANS FOR K ILNS Claims.

In small kilns such as may be used by artists or by persons in pursuit of a hobby, the time required for satisfactory firing of objects within a kiln is ordinarily ascertained by visual observation of what is known as a pyrometric pile or cone. The cone, located within the kiln, has to be watched in the course of the firing through a transparent pane within the wall of the kiln, and when the cone is sufficiently softened by the heat within the kiln so that its top turns downwardly upon itself in a hairpin turn, it is an indication that the firing is complete, whereupon the heat applied to the kiln is cut off manually.

It was in order to eliminate the necessity (if this observation of the cone and to eliminate the danger of having the heat turned on either too early or too late that I have devised my improvement. The improvement makes it possible to have the heat turned off at the right time, especially since the means employed by me call for the use of a pyrometric cone which except for the necessity of watching it, as mentioned above, has proved itself satisfactory and reliable.

I shall now describe my improvement with reference to the accompanying drawing in which:

Fig. 1 is a perspective View of my device with parts broken off in order that the details of the construction may be better disclosed;

Fig. 2 is a longitudinal sectional view of my device, the view including parts shown in a side elevation;

Fig. 3 discloses elements included in Fig. 2 but shows some of them in different operative positions;

, Fig. 4 is a front elevational view of elements of my device as they are placed within the kiln;

Fig. 5 shows the same View but with parts in different operative positions.

Similar numerals refer to similar parts throughout the several views.

The assembled device is best shown in Fig. 1, disclosing parts located on the outside of the kiln to which it is applied, parts within the kiln, and intermediate elements positioned within an aperture in the wall of said kiln. All said parts and elements are preferably made of metal.

Located on the outside in abutment with the wall of the kiln is a vertical plate Ill supporting a box H which houses an electric switch of a standard design, by means of which switch electric current may be cut off by a pivoted arm actuated from outside. As no novelty is claimed in the structure of the switch, no further description thereof seems to be necessary beyond what may be said in the course of this specification.

Hinged to the front wall or plate l2 of the box by means of pillow blocks l3 and pintels I4 journalled therein is an arm l5 normally extending vertically from said pillow blocks, the arm being provided at its lower end with an outwardly-projecting spur l6. Directly below the lower end of said arm IS the front wall ll! of the box I is provided with an aperture displaying a plate 8 within the box, to which plate reference will be had hereinbelow.

The top of arm I5 is of a solid, heavy construction to cause said arm, unless detained in its upwardly-extending position, to swing downwardly by gravity. The top I9 includes two vertical flanges 20 disposed in a spaced, parallel relation to each other. A sliding plate 2| fitting into the space between said flanges is cut off horizontally at the top, as shown at 22, and is provided at the bottom with an outwardly-extending lip 23 for manual operation thereof.

A vertical slot 24 within said plate 2| permits application of a screw 25 which passes through said slot to be threaded into the body of the top IQ of said arm IS. A washer 26 seated on the shaft of the screw and abutting plate 2| from outside serves to retain on the screw one end of a coiled spring 27, while the opposite end thereof is kept in place by the head of said screw. Numeral 28 shows a screw designed to limit the downward movement of the sliding plate 2|.

At the top, above said box I I, plate l0 contains a circular aperture 29. Fitting into said aperture is a tube 30 threaded on the outside. A part of the tube projects through said aperture 29 outwardly, that is, in the direction of the switch box. Threaded upon said part is a nut 3|, the nut being plugged at its outer end by a disc 32 which contains an axially-located opening 33.

Loosely fitting into said opening is a neck portion 34 of a cylindrical block 35 having an axial bore 36. The block serves as a means of supporting a standard shaft 31 which passes through said bore 36 and may be secured therewith against displacement by a set screw 38. One end of the shaft extending in the direction of arm |5 supports a sliding member 39 having a disc-like flange 40. The flange bears from outside against the top of sliding plate 2|. Numeral 4| indicates a set screw within said member 39.

Referring again to the above-said tube 30, it will be noted that it is disposed axially within a sleeve 42, the sleeve being threaded inwardly, as shown at 43, permitting a co-operative engagement with said tube 30. The sleeve carries at its outer end what may be designated as a clamping plate 44. The relative positions of plate l and said clamping plate 44 with respect to the wall 45 of the kiln is shown in Fig. 2, the wall being provided with a circular hole 46 transversely to the thickness thereof. The inner threading of said sleeve 42 and the outer threading of tube 36 permits said plates 44 and ID to be spaced from each other to correspond to the thickness of the wall 45 of the respective kiln.

The outer end of the sleeve which is pressfitted into an opening 46 in a clamping plate 4llv is closed by a plate A! the marginal portions of which are secured to the outer face of; plate M. A vertical gate 48 within said plate 41 is wide enough to permit rod 31 to pass through it, as shown in the drawings. Welded to the outer face of plate A l are two brackets 49:, each citric-brackets including a horizontal strip 50, the. strips being disposed at the same level but being spaced from each other and straddling said gate 48.

Seated upon rod ill at the end projecting through said. and adjoining plate 4'! is a disc like weigi t iii. A set screw -2 penetratesthe disc radially for a frictional engagement with the rod and. serves to hold the disc against displacement.

To complete the description of my device I wish to add that the pyrometric cone or pile used in conjunction with my device is marked 53. It must be stated here that pyrometric cones come in a number of varieties to fit specific conditions and requirements as to their initial plasticity in response to a definite degree of temperature, as obviously items of slender structure or one kind of clay may require less heat or a lesser period of exposure to heat than items of heavier structure and of a different substance.

I shall now describe the manner in which my device may be used. First, a cone of a suitable variety is selected for the specific task, the cone being of. the same variety which has been used in the kiln for visible observation. of its contents, as already described in this specification. The cone is placed lengthwise upon two horizontal strips 5a]. For the first firing of the objects in the kiln equipped with my device it is advisable to place the base of the. cone flush with the lateral of one of the strips. Next, rod 31 is. allowed to drop crosswise upon the cone, in which position it will be held by weight 5|. Assuming thatarm l5 in its normal upright position,,the sliding plate 2! is shifted upwardly against rod 3'? until the upper edge 22 of said plate will bear firmly against said rod, pressing the opposite end of the rod against the top of the pyrometric cone- To prevent the plate from sliding down, screw 25 is tightened against the outer surface thereof. While the rod is in this position the flange of the sliding member 39 which is seated. on the rod will hear from outside against the top of said sliding plate 2 l.

Assuming now that the firing of objects within kiln has been started and that the required temperature within the kiln has been kept. for a sufficient time to soften the cone, rod 31, weighed by disk 5!, will cause the cone to sag midway its length, as shown in Fig. 5. As with the sagging cone, the end of rod 3'5 resting thereon will sink below its original level shown in Fig. 4 to the level shown in Figs. 3 and 5, the opposite end of the rod will swing upwardly, as shown in 3, lifting member 39 out of contact with plate 22 mounted on arm Unchecked by flange 40 on said member 39,

arm l5 will swing away from its hinged lower portion from plate l2, causing spur Hi to enter aperture [1 and to depress the movable plate l8, thereby opening the switch. As a result thereof electric current supplied to the source of heat for the kiln will be cut off.

If it should appear that the pyrometric cone used in. conjunction with my device has softened too soon as measured by the pyrometric cone placed within the kiln for visual control, the next cone used in my device may be shifted lengthwise so as to wedge up rod 31 from below by said. cone. at. a. point where its thickness is somewhat smaller than on the first trial. The longitudinat shift of the cone may be gauged with respect to one edge of the horizontal strip 54k whichsupports the thicker end of the cone.

Reversely, if the firing lasted beyond the peiod actually needed, thecone may be shifted in the opposite direction, exposing a thicker portion for contact with the rod.

While in the description of my device I have referred to electric means of heating the kiln, it will be obvious that the switch forming a part of my device may control other means of supplying heat, such as gas. In such a case the switch would control electric current employed to operate a valve which supplies gas to a burner.

It will be understood that some changes may be made in the construction ofmy' device without departing from the inventive principle disclosed herein.

,What I, therefore, wish toclaim is as follows:

1. In combination with a kiln having a transverse aperture in its wall, two plates adapted to clamp said well therebetween, a tube disposed in said aperture and joining'the two plates, an electric switch mounted on the outside plate and including an arm disposed normally in a vertical position but hinged at its' lower; end and weighted at the top to cause it to swing down. unless restrained, bracket means mounted on the, inside plate and including two horizontal strips laterally spaced from, each other at. a. level below one end of the tube but parallel thereto, the

strips being adapted to support a pyrometric cone in a substantially horizontal position, a rod within the. tube, pivoted within the tube at. its end adjoining the outside plate, a disc-like member supported by the rod, the member being adapted to engage the upper end of said arm. to prevent its swing. downwardly but to release said arm on the swing of the adjacent end of the rod. upwardly, the opposed end of. the rodv being adapted. to rest on the pyrometric cone midway of its length and. above they spacing between said horizontal strips, weight means. on. the part. oi. the rod adjoining the inside plate to cause the rod to bear against. the. upper surface of. said! cone and to. swing. below the. level of. said upper surface with the sagging of the pyrometric cone. on exposure to heat.

2.. In combination with a kiln having a trans-- verse aperture in its wall, tubular means within said aperture, the tubular means being adjusts able longitudinally, two horizontal strips-mounted on the inside of said wall below the level of the aperture, the strips being horizontally spaced from each other and extending inwardly into the kiln, an electric switch outside the kiln, the switch including a hinged arm normally disposed in an inoperative position but tending by gravity to swing into an operative position, a rod disposed within said tubular means but projecting therefrom at each end thereof, the rod being" pivotally mounted therewithin, one end of said rod being weighted to bear from above upon a pyrometric cone supported on said horizontal strips at a point midway of said strips, the other end of the rod including means in a sliding contact with the arm to hold it in its inoperatiye position, the rod being adapted to swing down at the weighted end in response to the sagging of the cone by exposure to heat and at its other end to release the arm into its operative position to cut off means supplying heat to the kiln.

3. A device to actuate a switch controlling electric current for means to supply heat to a kiln, which kiln is provided with a transverse aperture in its wall, said device including two horizontal strips horizontally spaced from each other and mounted inside the kiln on the wall thereof, the strips being adapted to support a pyrometric cone in a substantially horizontal position, a switch outside the kiln but associated therewith, the switch including a hinged arm adapted to swing by weight into an operative position, a rod disposed within said aperture and pivoted at a point between its ends, one end of the rod being weighted down to hear from above against a pyrometric cone resting horizontally on the two strips and spanning the space therebetween, the other end of the rod including flange means for engagement with the arm to hold it in its inoperative position, the means being adapted to release the arm when the weighted end of the rod has swung to a level below the initial position of the rod on the cone as a result of the softening of the cone by exposure to heat, causing the other end of the rod to disengage said arm.

4. In combination with a kiln having a transverse aperture in its wall, a device to actuate a switch in an electric circuit controlling heatsupplying means for said kiln, the device including two horizontal strips secured to the wall of the kiln on the inside thereof, the strips being horizontally spaced from each other at the same level and being adapted to support the opposite ends of a pyrometric cone in a substantially horizontal position, an electric switch outside the kiln but associated therewith, the switch including a.

hinged arm adapted to be swung into an operative circuit-opening position, a rod extending from outside through said aperture and pivoted intermediate its ends, one of the ends being weighted to hear from above against the midportion of the cone and to sink lower therewith with the sagging body of the cone in response to the exposure of said cone to heat, the other end of the rod serving to normally keep the arm in its inoperative position but being adapted to release said arm into its operative position on being swung up by the lowering of the weighted end of said rod.

5. In combination with a kiln having an aper ture in its wall, a device to actuate a switch in an electric circuit controlling heat-supplying means for said kiln, the device including two horizontal strips secured to the wall of the kiln on the inside thereof, the strips being spaced from each other at the same level, a pyrometric cone resting on said strips crosswise thereof and being adapted to be adjustably shifted lengthwise upon said strips, an electric switch outside the kiln but associated therewith, the switch including a hinged arm adapted to be swung into an operative circuitopening position, a rod extending from outside through said apertur and pivoted to said wall intermediate its ends, one of the ends being weighted to bear from above against the portion of the body of the cone directly above the space between said strips, the other end of the rod being adapted by intermediate means to operat the switch.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 644,915 Holdcroft et al Mar. 6, 1900 972,353 Eskridge Oct. 11, 1910 1,187,083 Murray June 13, 1916 1,193,705 Lynch Aug. 8, 1916 2,555,864 Strange June 5, 1951 FOREIGN PATENTS Number Country Date 8,426 Great Britain of 1898 435,581 Great Britain June 25, 1934 

